Conventional urethane-type polymers are prepared by the reaction of a polyol or a polyol-based compound with an isocyanate, typically in the presence of a metallo catalyst, and a curing agent, such as an amine. Caprolactone-type polyol polymers have been suggested for reaction wtih isocyanates, such as TDI and MDI, in the presence of various metallic catalysts, such as organo metallic catalysts comprising tin, lead and zinc and combinations thereof with a triethylene diamine curing agent (that is, Dabco, a trademark of Air Products and Chemical Co.). However, when these catalysts are employed with an aliphatic isocyanate, together with a caprolactone polyol, a very slow-curing polymer results. While various combinations of the metallic catalyst may vary the curing time, such as the combination of both lead and tin, the reaction time to prepare the aliphatic isocyanate base polymers is still quite slow, typically 2 to 24 hours or more.
Where the caprolactone polyols have been reacted with TDI or MDI in the presence of a tin catalyst and a triethylene diamine curing agent, the caprolactone polyol supplier has reported that polyurethanes of superior properties are produced. However, it has been found that such polymers provide for only flexible-type polymers, and that such polymers produce porous-type films and coatings.
Solid polyurethanes, both elastomeric and rigid, have been produced in many different formulations as polyesters and polyethers; however, polyurethanes of zero or substantially zero porosity and polyurethanes in thin-film or coating form, on which a vacuum could be pulled and held, have not been available commercially. Rim-molding and open spray-molding applications can usefully employ both rigid and flexible polymeric materials without porosity, such as for applications like roof membranes, spraying films onto metals for corrosion control, boats, bath tubs and other film and coating use applications.
Therefore, it is desirable to provide solid polyurethanes which may be used in flexible or rigid form in RIM-molding and open mold-spraying techniques, and which polyurethanes are fast-reacting and which may also have low or zero gas porosity.